1. Field of the Invention
This invention relates to a method of and an apparatus for forming a pattern of fluorescence on a color CRT by using electron beams.
2. Description of the Prior Art
Generally, the fluorescent surface of a color CRT is composed of a black light absorbing layer and a fluorescence layer. The fluorescence layer is formed in a pattern of, for example, stripes or dots, with spaces between the stripes or dots of fluorescence being filled with the black light absorbing layer.
FIG. 10 of the accompanying drawings shows a prior exposure apparatus for forming a pattern fluorescence, which is disclosed in Japanese Patent Laid-Open Publication No. 9030/1985.
In the prior exposure apparatus, a face panel 1 is supported on a plate 3 formed on an upper portion of a housing 2 in which a high-voltage mercury-arc lamp serving as a light source 4 for exposure is disposed. A shadow mask 5 is attached to the face panel 1 so that a fluorescence layer can be formed in a predetermined pattern. The shadow mask 5 has a plurality of openings 5a, for the passage of light from the light source 4, in a pattern corresponding to the pattern of fluorescence to be formed.
A correcting lens 6 and a filter 7 are disposed between the face panel 1 and the light source 4. The correcting lens 6 serves to deflect the light from the light source 4 in a correct direction, while the filter 7 allows, of the whole light coming from the light source 4, only partial light of a particular wavelength to pass.
The light source 4 is movable, according to the color of the fluorescence to be exposed, to a predetermined position where exposing is to take place.
Consequently, the light from the light source 4 is subjected to a predetermined deflection by the correcting lens 6, and only the partial light having a particular wavelength is allowed to be irradiated over the face panel 1 by the action of the filter 7. However, since the shadow mask 5 is disposed behind the face panel 1, only the light passed through the openings 5a of the shadow mask 5 reaches the face panel 1, and as a result, exposing will take place.
The method in which a pattern of fluorescence is formed by using the exposure apparatus of FIG. 10 will now be described with reference to FIGS. 11a through 11i.
As shown in FIG. 11a, firstly, a predetermined pattern of black light absorbing layer 10 is formed on the face panel 1 in a known method. Thus the block light absorbing layer 10 is formed in the form of stripes, for example.
Then, as shown in FIG. 11b, a slurry 12r is applied over the black light absorbing layer 10 formed on the face panel 1. This slurry 12r is a mixture of a liquified photosensitive resin and a red fluorescence. The slurry 12r is dried after having been applied over the black light absorbing layer 10.
As shown in FIG. 11c, the face panel 1 is then mounted on the plate 3 of the exposure apparatus of FIG. 10, and the shadow mask 5 is attached to the face panel 1, whereupon exposing takes place.
After exposing, the face panel 1 is removed from the exposure apparatus, the inner surface of the face panel 1 is washed, for example, by spraying hot water. Thus, as shown in FIG. 11B, the slurry 12r on the non-exposed portion is removed, while only the exposed portion, which is printed by the light passed through the openings 5a, remains.
By the foregoing, a red fluorescence pattern has been formed.
To form a green fluorescence pattern, as shown in FIG. 11e, a slurry 12g including a green fluorescence is applied over the face panel 1 and is then dried, whereupon exposing takes place as shown in FIG. 11f.
Then the inner surface of the face panel 1 is washed to remove the slurry 12g on the non-exposed portion. As a result, a pattern of the green fluorescence remains as shown in FIG. 11g.
Likewise, as shown in FIG. 11h, a slurry 12b including a blur fluorescence is applied over the face panel 1 and then dried, whereupon exposing takes place as shown in FIG. 11i. Then the slurry 12b on the non-exposed portion is removed by washing.
By the foregoing, as shown in FIG. 12, the fluorescence patterns of three colors, i.e. red, green and blue, have been formed on the face panel 1. FIG. 13 is a fragmentary plan view showing the pattern including three-color sets of fluorescence strips.
However, the foregoing prior method and apparatus have the following problems.
It is necessary to attach and detach the shadow mask to and from the face panel 1 every time a pattern of each kind of fluorescence is formed, which is laborious and time-consuming, thus causing a reduced rate of production. Further, overlapping over the adjacent fluorescence patterns would be caused by the error in the attaching position of the shadow mask and the light diffraction at the openings of the shadow mask so that an accurate pattern could not occasionally be formed.
With the prior exposure apparatus, a correcting lens is necessary so that dust attached to this correcting lens would be projected, thereby causing a fault pattern. This gives bad influences to the clearness of a color CRT. It is also necessary to change the correcting lens every time the kind of the CRT is changed, which is laborious and time-consuming in adjusting.